Method for sealing electric terminal assembly

ABSTRACT

A method is disclosed of sealing a wire terminal assembly including a conductive cable core connected to a conductive terminal along a conductive connection interface. According to the method, a coating composition is dispensed over the conductive connection interface. The coating composition includes (1) a polymerizable compound with an unsaturated bond, and (2) a free radical photoinitiator. The dispensed coating composition is then subjected to actinic radiation for a duration of less than 0.7 seconds.

BACKGROUND

The field of this disclosure relates to an electrical connection betweena cable and a terminal.

Cable terminal connections are commonly used to facilitate electricalconnections between various electrical or electronic components andsub-components. The designs are myriad, and common features include aphysical and electrically-conductive connection between a terminal andan electrically-conductive cable core. It is sometimes desirable to sealthis electrically-conductive connection against outside contaminantssuch as dirt and moisture in order to maintain the integrity of theelectrically-conductive connection.

Conductive cable cores and terminals are commonly made of conductivemetal(s). Interest in weight savings and cost savings in variousapplications such as automotive electrical wiring applications have madealuminum based cables an attractive alternative to copper based cables.However, some wiring and electrical connectors may remain copper based.Thus, there may be a transition somewhere in the electrical circuitbetween an aluminum based portion of the circuit and a copper basedportion of the circuit. Often this transition may occur at the terminalbecause the terminal may include copper (e.g., tin-plated copper) basedfor reasons of size and complexity of shape that can be more easilyachieved with copper based materials over aluminum based materials. Acrimp interface connection of metal cable core (e.g., aluminum) to adifferent metal terminal (e.g., copper) can produce galvanic corrosionat the interface of the metal of lower nobility if an electrolyte suchas salt water is present.

Various materials and techniques have been proposed to protect frommoisture at electric cable terminal connections. However, since even asmall amount of exposed metal at the interface can be susceptible to theeffects of moisture, including significant galvanic corrosion, therecontinues to be a need for new approaches to providing robust terminalconnections for electric wire and cable.

SUMMARY

In accordance with some embodiments, there is a method of sealing a wireterminal assembly comprising a conductive cable core connected to aconductive terminal along a conductive connection interface. Accordingto the method, a coating composition is dispensed over the conductiveconnection interface. The coating composition comprises a polymerizablecompound comprising an unsaturated bond, and (2) a free radicalphotoinitiator. The dispensed coating composition is then subjected toactinic radiation for a duration of less than 0.7 seconds.

BRIEF DESCRIPTION OF DRAWINGS

The subject matter herein is particularly pointed out and distinctlyclaimed in the claims at the conclusion of the specification. Theforegoing and other features, and advantages of the invention areapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a schematic depiction in a perspective view of an exampleembodiment of a wire terminal assembly; and

FIG. 2 is a schematic depiction in a cross-sectional view of an exampleembodiment of a coated portion of a terminal wire assembly.

DETAILED DESCRIPTION

Referring now to the Figures, FIG. 1 depicts an exemplary embodiment ofa cable 10 having an insulative outer cover 12 and a conductive core 14.The conductive core can comprise a first metal, which can include metalalloys. The conductive core 14 is depicted in FIG. 1 as comprising agrouping of individual strands 15 bundled and/or twisted together, butcould also have other configurations such as a mono-element metal core.An end portion of an insulative outer cover 12 is removed to expose alead 16 of the conductive core 14. A terminal 22 has a rearward portion84 including a pair of insulation crimp wings 36 and a pair of corecrimp wings 38 with a notch or gap 40. In some embodiments, the terminal22 can comprise a second metal, which can include metal alloys. Theinsulation and core crimp wings 36 and 38 are crimped into a physicalconnection with cable 10 such that terminal 22 is secured to insulativeouter cover 12 and makes electrical contact with lead 16 of theconductive core 14. Voids 42 may be formed between individual strands 15of the conductive core 14 before or after terminal 22 is crimped ontocable 10. Core crimp wings 38 may optionally include serrations 17 toenhance the bite of core crimp wings 38 into the lead 16.

As further shown in FIG. 1, a coating applicator 100 dispenses a coatingcomposition 102 at the interface of the lead 16 and the terminal 22. Thecoating applicator can be any type of applicator, including but notlimited to one or more spray nozzles, brushes, rollers, or jet heads. Insome embodiments, the spray applicator includes one or more jet heads.Jet applicators are known, and are described for example in U.S. Pat.Nos. 5,320,250; 5,747,102; and 6,253,957, and US Appl. Pub. No.2016/0089681 A1, the disclosures of each of which are incorporatedherein by reference in their entirety. In some embodiments, the jethead(s) can apply the coating composition while moving in apredetermined pattern above the terminal. The specific dispensingparameters can vary widely depending on the size and configuration ofthe terminal assembly being sealed. In some embodiments of interest, jetdispensing can be performed with a linear dispensing velocity in a rangehaving a lower end of 0.1 mm/s, more specifically 5 mm/s, and even morespecifically 10 mm/s, and an upper limit of 500 mm/s, more specifically100 mm/s, and even more specifically 50 mm/s. In some embodiments ofinterest, the jet head(s) can dispense and apply fluid with a frequencyrange with a lower end of 1 Hz, more specifically 125 Hz, and an upperlimit of 500 Hz, more specifically 250 Hz. In some embodiments ofinterest, the jet head(s) dispense numerous dots to form a uniformcoating. In some embodiments, drop sizes between 2 nl and 2 ml, morespecifically between 0.25 ml and 2 ml. The dispensing pulse can be setso that the valve is continually open, creating a steady stream with amaximum volume limited to the amount of material contained in the valve,e.g., 2 ml. In some embodiments, an actinic radiation source 104 such asan ultraviolet (UV) radiation source can be integrated with the coatingapplicator 100.

As mentioned above, the coating is applied to the conductive connectioninterface at any portion where it can be exposed to moisture. There mayof course be some portions of the interface that are not directly coated(e.g., where a bit or gripping portion of the core crimp wings 38 isdeeply engaged into and sealed against the conductive core 14 so thatneither moisture nor the coating composition could penetrate); however,in some embodiments, the coating covers and seals all of the exposedportions conductive connection interface and adjoining exposed portionsof the cable core and terminals. In some embodiments, the coating coversand seals all portions of the conductive cable core exposed outside ofthe insulating outer cover. As depicted in FIG. 1, the coatingapplicator 100 is applying the coating composition to the area of gap40. In some embodiments of FIG. 1, the coating composition is applied tocover any one or combination or all of: the exposed portion of theconductive core 14 in the gap 40, the core crimp wings 38, the interface28 between the core crimp wings 38 and the conductive core 14, acorresponding interface (not shown) between the core crimp wings 38 andthe conductive core 14 in the area of gap 40, and the exposed portion ofthe conductive core 14 protruding past the core crimp wings 38(including any voids 42 between strands 15, if present).

In some embodiments, a first metal of the core and a second metal of theterminal can be the same or can be different alloys of the same metal.In some embodiments, the first and second metals can be differentmetals. In some embodiments, the coating is applied to seal anelectrically conductive connection interface between metals havingdifferent electrode potentials (defined as the electromotive force of acell in which the electrode on the left is a standard hydrogen electrodeand the electrode on the right is the electrode in question) in order toprovide protection against moisture penetration that can cause galvaniccorrosion. The difference in electrode potential needed to causegalvanic corrosion can vary widely based on a number of factors such assalt content in the penetrating moisture, surface areas of the exposedmetals, distance through the liquid electrolyte between the metals,temperature, etc. Electrode potential differences commonly associatedwith galvanic corrosion can range from 0.15 to 1.8 volts. Examples ofmetal pairings where difference in electrode potential can lead togalvanic corrosion include aluminum and copper (e.g., aluminum cablecore and terminals of copper or tin-plated copper). In some embodiments,the terminal can be formed from a metal that is more noble than thecable core metal. In some embodiments, the terminal can be formed from ametal that is less noble than the cable core metal. In some embodiments,the first and second metals can have the same electrode potential or canbe the same metal. In such embodiments, the applied coating can stillseal against moisture that can cause oxidation, even if there is nopotential for galvanic corrosion.

In some embodiments, the process parameters of the application, and/orthe properties of the coating composition (e.g., viscosity) can beadjusted or maintained to promote formation of a conformal coating atthe interface between the lead and the terminal, including any gapsbetween the interface and the lead, or in adjacent areas (e.g., topromote coverage or filling of any voids 42 strands 15). In someembodiments, a conformal coating can be defined as one that conforms tothe contours of the underlying substrate rather than fill gaps andlevelling to form a level surface. In some embodiments, a coating suchas a conformal coating can have a thickness in a range having a lowerend of 50 μm, more specifically 75 μm, and even more specifically 100μm, and an upper limit of 5 mm, more specifically 2 mm, morespecifically 1 mm, and even more specifically 0.5 mm. For jetapplication as described above, useful viscosities for promotingconformal coatings can include those viscosity ranges mentioned above.An example of a coating such as a conformal coating is schematicallydepicted in FIG. 2, where a substrate comprising a portion of theconductive core 14 and the terminal 22 are coated with a coating 102′.

After application, the coating composition is cured via a free radicalpolymerization in response to activation of the photoinitiator. In someembodiments, an actinic radiation source 104 such as a UV light sourcecan be integrated with coating applicator 100 as depicted in FIG. 1,facilitating sequential application of the coating composition followedby exposure to UV light. In some embodiments, the source of actinicradiation (e.g., the actinic radiation source 104) can be positionwithin 10 mm of the coating composition. Theoretically, there is nospecific minimum distance required between the source of actinicradiation, but in some embodiments practical considerations ofpositioning the source of actinic radiation can impose a minimumspecified distance such as 1 mm.

Although this disclosure is not limited to or by any particular theoryor mode of operation, it is believed that the specified actinicradiation exposure levels of free radical photoinitiator may contributeto promotion of relatively rapid polymerization at or near the surfaceof the coating exposed to radiation, and a slower rate of polymerizationbelow the surface proximate to the conductive connection interface. A UVabsorber may also contribute to this effect. Rapid polymerization at ornear the surface may allow the coating to set up rapidly to provideefficient and rapid manufacturing and resistance to subsequentcontamination from airborne contaminants, while the not fully curedinterior of the coating can continue to provide flowability to penetrateand coat interstitial spaces around the conductive connection interface.In some embodiments, the coating can provide properties such as waterresistance, flexibility, temperature-resistance, etc., while the monomercan contribute adjustment of coating composition properties such asviscosity and adhesion to provide for proper deposition and flow of thecoating composition to all desired areas of the substrate, and theaddition polymerization during cure, with the presence ofhighly-reactive free radical species such as those produced during thepolymerization of (meth)acrylates and/or acrylic acid, can contribute toadhesion to and integration of the coating with the substrate.

As mentioned above, the coating composition is exposed to actinicradiation for a duration of less than 0.7 seconds. In some embodiments,the duration of actinic radiation exposure can be in a range with a lowend of >0 seconds, 0.05 seconds, 0.1 second, 0.15 seconds, or 0.2seconds, or 0.25 seconds, and an upper end of <0.7 seconds, 0.6 seconds,0.5 seconds, or 0.4 seconds. The above lower and upper range endpointscan be independently combined to disclose a number of different ranges,and their disclosure above constitutes a disclosure of each possiblecombination. In some embodiments, the actinic radiation comprises UVradiation. In some embodiments, the actinic radiation includes a peakintensity at a wavelength in a range with a low end of 300 nm, 340 nm,380 nm, or 390 nm, and a high end of 400 nm, 410 nm, 450 nm, or 490 nm.The above lower and upper range endpoints can be independently combinedto disclose a number of different ranges, and their disclosure aboveconstitutes a disclosure of each possible combination. In someembodiments, the coating is exposed to an amount of energy from theactinic radiation in a range with a low end of 0.5 joules, 1.0 joules,1.5 joules, or 2.5 joules and a high end of 15 joules, 16 joules, or 17joules. The above lower and upper range endpoints can be independentlycombined to disclose a number of different ranges, and their disclosureabove constitutes a disclosure of each possible combination.

As mentioned above, the coating composition includes a polymerizablecompound comprising an unsaturated bond. Examples of such compoundsinclude monomers such as alkyl (meth)acrylates; alkoxyalkyl(meth)acrylates; (meth)acrylonitrile; vinylidene chloride; styrenicmonomers; alkyl and alkoxyalkyl fumarates and maleates and theirhalf-esters, cinnamates; and acrylamides; N-alkyl and aryl maleimides(meth)acrylic acids; fumaric acids, maleic acid; cinnamic acid; andcombinations thereof. In some embodiments, the monomer comprises a(meth)acrylate monomer or acrylic acid. More specifically, examplemonomers can include are not limited to any particular species butincludes various monomers, for example: (meth)acrylic acid monomers suchas (meth)acrylic acid, methyl(meth)acrylate, ethyl (meth)acrylate,n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl(meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate,n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl(meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate,2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate,dodecyl (meth)acrylate, phenyl (meth)acrylate, toluyl (meth)acrylate,benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl(meth)acrylate, stearyl (meth)acrylate, glycidyl (meth)acrylate,2-aminoethyl (meth)acrylate, -(methacryloyloxypropyl)trimethoxysilane,(meth)acrylic acid-ethylene oxide adducts, trifluoromethylmethyl(meth)acrylate, 2-trifluoromethylethyl (meth)acrylate,2-perfluoroethylethyl (meth)acrylate,2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl(meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethylmethyl(meth)acrylate, 2-perfluoromethyl-2-perfluoroethylethyl (meth)acrylate,2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl(meth)acrylate and 2-perfluorohexadecylethyl (meth)acrylate; styrenicmonomers such as styrene, vinyltoluene, α-methylstyrene, chlorostyrene,styrenesulfonic acid and salts thereof; fluorine-containing vinylmonomers such as perfluoroethylene, perfluoropropylene and vinylidenefluoride; silicon-containing vinyl monomers such asvinyltrimethoxysilane and vinyltriethoxysilane; maleic anhydride, maleicacid, maleic acid monoalkyl esters and dialkyl esters; fumaric acid,fumaric acid monoalkyl esters and dialkyl esters; maleimide monomerssuch as maleimide, methylmaleimide, ethylmaleimide, propylmaleimide,butylmaleimide, hexylmaleimide, octylmaleimide, dodecylmaleimide,stearylmaleimide, phenylmaleimide and cyclohexylmaleimide;nitrile-containing vinyl monomers such as acrylonitrile andmethacrylonitrile; amido-containing vinyl monomers such as acrylamideand methacrylamide; vinyl esters such as vinyl acetate, vinylpropionate, vinyl pivalate, vinyl benzoate and vinyl cinnamate; alkenessuch as ethylene and propylene; conjugated dienes such as butadiene andisoprene; vinyl chloride, vinylidene chloride, allyl chloride, allylalcohol, etc.

In some embodiments, the polymerizable compound can comprise an oligomercomprising at least two active double bonds. As used herein, an activedouble bond is a double bond that is reactive with free radical monomerunits during free radical polymerization. Typically such double bondsare in end groups at a terminus of an oligomer backbone molecule, butcan also be disposed in side groups appended to the oligomer. In someembodiments, the oligomer comprises an active double bond at each of thetwo termini of the oligomer backbone. In some embodiments, the oligomercan include one or more double bonds disposed in a side groups appendedto the oligomer backbone. The implementation of side group double bondsallows for more than two active double bonds in the oligomer molecule,which can provide molecular branching loci in the polymerizate.

Oligomers can be assembled from conventional monomer building blocks aswith polymers, but with process and ingredient controls used to controlmolecular weight (e.g., common techniques for controlling molecularweight growth include but are not limited to stoichiometric excess ofone type of monomer for condensation reactions, use of monofunctionalcapping agents, polymerization catalyst quenchers, or reaction quenchingprocessing such as a reduction of temperature). Oligomers and polymersare both characterized in the IUPAC Gold Book by their property of nosignificant change in properties by addition or removal of one or a fewmonomer units, and are distinguished by oligomers being of intermediatemolecular mass and polymers being of high molecular mass. In someembodiments, the oligomers can have a degree of polymerization with anumber of monomer units in a range having a low end of 5 monomer units,more specifically 10 monomer units, more specifically 20 monomer units,more specifically 50 monomer units, and even more specifically 100monomer units, and an upper limit of 1000 monomer units, morespecifically 500 monomer units, more specifically 200 monomer units,more specifically 150 monomer units, more specifically 125 monomerunits, and even more specifically 100 monomer units. The above lower andupper range endpoints can be independently combined to disclose a numberof different ranges, and their disclosure above constitutes a disclosureof each possible combination. In some embodiments, the oligomer has adegree of polymerization of 100-500 monomer units.

In some embodiments, the oligomer can be a difunctionally-unsaturatedurethane oligomer, such as a urethane methacrylate. Such oligomers canbe formed from polyurethane monomer building blocks of polyisocyanatesand polyols, with an unsaturated bond-containing mono-hydroxy compound(e.g., a hydroxyl-containing (meth)acrylate) acting as a capping agentwith respect to the polycondensation urethane chain-building reaction.Examples of polyisocyanates include hexamethylene diisocyanate,isophorone diisocyanate, cyclohexane-1,4-diisocyanate, methylenebis(4-cyclohexylisocyanate), toluene diisocyanate, diphenylmethane4,4-diisocyanate, xylene diisocyanate, 1,4-phenylene diisocyanate,diisocyanates and triisocyanates of HDI-based oligomers, and otheraliphatic and aromatic isocyanates. Examples of polyols include diolssuch as ethylene glycol, propylene glycol, 1,3-propanediol, 1,2, 1,3 or1,4 butanediols, 2-methyl-1,3-propane diol (MPDiol), neopentyl glycol(NPG), alkoxylated derivatives of such diols, polyether diols, polyesterdiols, and the like. Higher functional polyols can include trimethylolpropane (TMP), PETA, di-TMP, di-PETA, glycerol, alkoxylated derivativesthereof, and the like. A mono-hydroxy-containing unsaturated compoundsuch as a hydroxyl-containing (meth)acrylates can be used to provide theoligomer with a terminal group comprising an unsaturated bond. Examplesof hydroxyl-containing (meth)acrylates are hydroxyethyl (meth)acrylate,hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate,trimethylolpropane mono- and di-(meth)acrylate, pentaerythritol mono-,di-, tri-(meth)acrylate, dipentaerythritol mono-, di-, tri-, tetra-, andpenta-(meth)acrylate, neopentyl glycol (meth)acrylate, hexanediolmono(meth)acrylate, tris(2-hydroxyethyl)isocyanurate mono- anddi(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethyleneglycol mono (meth)acrylate, polypropylene/polyethylene glycolmono(meth)acrylate, polybutyl glycol mono(meth)acrylate,polytetramethylene glycol mono(meth)acrylate, hydroxy polycaprolactonemono(meth)acrylate, and ethoxylated and propoxylated derivativesthereof. The terminal group on the oligomer can also include unsaturatedgroups other than acrylate groups. For example, U.S. Pat. No. 6,559,260discloses urethane oligomers terminated with allyl groups.

Urethane oligomers can be prepared with or without catalysts. In thecase where catalyst is used, various different catalysts can be used.Catalyzed reactions are desirable due to the shortened reaction time andfewer by-products. Typical catalysts which may be used for this reactionare amines and metal-based catalysts. Some examples include dibutyltindilaurate, 1,4-diazabicyclo[2.2.2]-octane (DABCO),1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU), N,N-dimethylcylohexylamine(DMCA), tetramethyltin, tetrabutyltin, tetraoctyltin, tributyltinchloride, dibutyltin dichloride, dimethyltin oxide, trimethyltinchloride, dimethyltin dichloride, trioctyltin chloride, dibutyltinoxide, dibutyltin diacetate, butyltin trichloride, dioctyltindichloride, dioctyltin oxide, dioctyltin dilaurate, and dioctyltindiacetate. Zinc, iron, bismuth, and zirconium complexes similar to—thosetin-based complexes set forth above could also be used as catalysts.Urethane oligomers can be formed by reacting the polyol(s) with a molarexcess of the polyisocyanate(s) followed by reacting the resultantisocyanato-terminated product with the hydroxy functional(meth)acrylate(s), or in an alternative method the polyisocyanate(s),hydroxy functional (meth)acrylate(s), and metal salt polyol(s) can bemixed and reacted in one step. In the condensation reaction, one can usebetween 0.5 and 2.0, preferably 0.75 and 1.5, more specifically between0.9 and 1.1 equivalents of isocyanate for each equivalent of hydroxyl.In this manner, free alcohol or free isocyanates remaining in the finalmaterial can be avoided. The final, condensed product will include(meth)acrylate functionalities that can be cured with free radicalmechanism such as peroxides or radiation curing processes.

In some embodiments, the oligomer can include aliphatic hydrocarbonchain segments of 4-10 carbon atoms, more specifically 6-8 carbon atoms.Such aliphatic segments can be incorporated into the oligomer chainthrough the monomer (e.g., C6 segments in hexamethylene diisocyanate, C5segments in 1,5-pentanediol).

In some embodiments, the oligomer can include polyester segments. Suchsegments can be prepared in a polycondensation reaction of polyol withpolyacid. Polyols useful in preparing polyesters for use in thisinvention are polyfunctional alcohols of the type conventionallyutilized in polyester preparation. Such polyols include ethylene glycol,1,5-propanediol, propylene glycol, triethylene glycol, butylene glycol,glycerol, diethylene glycol, 1,4,6-hexanetriol, trimethylolpropane,trimethylolethane, dipropylene glycol, pentaerythritol, neopentylglycol, alkoxylated 2,2-bis(4-hydroxyphenyl) propane and the like.Although diols are generally utilized in the preparation of unsaturatedpolyesters, more highly functional polyols, i.e., polyols having afunctionality of three to five, can also be used. In addition, apolyethylenically unsaturated monomer such as dicyclopentadiene orBisphenol A dicyclopentadiene and derivatives thereof can be included.Examples of polycarboxylic acids optionally useful in preparingunsaturated polyesters used in this invention include phthalic acid,phthalic anhydride, isophthalic acid, tetrahydrophthalic acid,hexahydrophthalic acid, endomethylene tetrahydrophthalic acid, glutaricacid, tetrachlorophthalic acid, suberic acid, hexachloroendomethylenetetrahydrophthalic acid, sebacic acid, tetrahydrophthalic anhydride,succinic acid, adipic acid, and the like, wherein the term “acid”includes the corresponding anhydrides where such anhydrides exist.Terminal groups comprising unsaturated bonds can be provided withhydroxy (meth)acrylate chain terminators, or with unsaturatedmono-acids, including but not limited to maleic acid, citraconic acid,fumaric acid, glutaconic acid, itaconic acid, chloromaleic acid,mesaconic acid, and the like, wherein the term “acid” is used to includethe corresponding anhydrides where such anhydrides exist. Polyestermolecules can be formed through known transesterification condensationreaction and catalyzation techniques. Aliphatic segments can be includedin the polyacid (e.g., C8 segments in sebacic acid, C5 segments in1,5-pentane diol).

In some embodiments, the oligomer can have both polyurethane andpolyester segments. For example, a polyester diol can be prepared usingthe polyester-formation techniques and incorporated as part of thepolyol reactant in forming a urethane oligomer such as a urethaneacrylate oligomer.

Oligomers as described above are commercially available, and aredescribed in various US patent references, including US publishedapplication nos. US 2004/0054798 A1, US 2003/0149179 A1, US 2005/0154121A1, and U.S. Pat. Nos. 6,472,069, 6,559,260, 6,380,278, the disclosuresof each of which are incorporated herein by reference in their entirety.

As mentioned above, the coating composition includes greater than 4parts per hundred by weight of a free radical photoinitiator, based onthe total weight of polymerizable compound. Some free radicalphotoinitiators can produce free radicals by unimolecular fragmentationin response to exposure to external energy. The radicals are produced bya homolytic or heterolytic cleavage of a sigma bond in the molecule.Examples of this type of photoinitiator include but are not limited toperoxides, and peroxy compounds, benzoin derivatives (including ketoximeesters of benzoin), acetophenone derivatives, benzlketals,α-hydroxyalkylphenones and α-aminoalkylphenones, O-acylα-oximinoketones, acylphosphine oxides and acylphosphonates, thiobenzoicS-esters, azo and azide compounds, triazines (e.g., trichloromethyltriazines, tribromomethyl triazines, aryl iodides), and biimidazoles.

Some free radical photoinitiators can produce free radicals bybimolecular hydrogen abstraction in response to exposure to externalenergy. The hydrogen abstraction photoreactive group transforms to anexcited state and undergoes an intermolecular reaction with a hydrogendonor to generate the free radical, leading to the formation of a pairof radicals originating from two different molecules. Examples of thistype of photoinitiator include but are not limited to quinones,benzophenones, xanthones and thioxanthones, ketocoumarins, aromatic 1,2diketones, and phenylglyoxylates.

Photoreactive aryl ketones can include acetophenone, benzophenone,anthraquinone, anthrone, and anthrone-like heterocycles (i.e.,heterocyclic analogs of anthrone such as those having N, O, or S in the10-position), or their substituted (e.g., ring substituted) derivatives.Examples of aryl ketones include heterocyclic derivatives of anthrone,including acridone, xanthone, and thioxanthone, fluorone, which termsare defined herein as including their ring substituted derivatives. Thephotoreactive groups of such ketones are capable of photochemicalexcitation with the initial formation of an excited singlet state thatundergoes intersystem crossing to a triplet state. The excited tripletstate can insert into carbon-hydrogen bonds by abstraction of a hydrogenatom (from a support surface, for example), thus creating a radicalpair. Subsequent collapse of the radical pair leads to formation of anew carbon-carbon bond. If a reactive bond (e.g., carbon-hydrogen) isnot available for bonding, the ultraviolet light-induced excitation ofthe benzophenone, acetophenone or anthraquinone group is reversible andthe molecule returns to ground state energy level upon removal of theenergy source. Photoactivatable aryl ketones such as benzophenone,anthraquinone and acetophenone are of particular importance inasmuch asthese groups are subject to multiple reactivation in water and henceprovide increased coating efficiency.

Another class of photoreactive groups includes compounds having an Si—Sibond. The radicals generated upon the breakage photo-induced cleavage ofthe Si—Si bond to provide reactive sites. Examples of Si—Si bondcleavage can be found in J. Lalevee, M. El-Roz, F. Morlet-Savery, B.Graff, X. Allonas and J. P. Fouassier, “New Highly efficient RadicalPhotoinitiators based on Si—Si Cleavage” Macromolecules, 2007, 40,8527-8530, the disclosure of which is incorporated by reference in itsentirety. Examples of such photoinitiators include10,10′-bis(10-phenyl-10H-phenoxasilin (Sigma-Aldrich, St. Louis Mo.) and9,9′-dimethyl-9,9′-bis-9H-9-silafluorene.

Free radical photoinitiators are commercially available and include, forexample, IRGACURE compounds from BASF, H-Nu compounds from Spectra(e.g., H-Nu-470-LT5), and DAROCURE 1173 BASF. Free radical initiatorsinclude fluorones (including fluorone derivatives) as disclosed in U.S.Pat. Nos. 5,451,343, 5,395,862, the disclosures of which areincorporated herein by reference in their entirety.

As mentioned above, the coating composition includes an amount of freeradical photoinitiator, expressed as parts per hundred by weight basedon the total weight of monomer or other polymerizable compound (i.e.,based on the total weight of polymerizable compound) (phm), of at least4 phm. In some embodiments, the coating composition includes at least 6phm of free radical photoinitiator. In some embodiments, the coatingcomposition includes at least 8 phm of free radical photoinitiator. Insome embodiments, the coating composition includes at least 10 phm offree radical photoinitiator. In some embodiments, the coatingcomposition includes an amount of free radical photoinitiator in a rangewith a low end of >4 phm, or 6 phm, 8 phm, or 10 phm, and an upper endof 12 phm, 14 phm, or 16 phm. All possible combinations of theabove-mentioned range endpoints are explicitly included herein asdisclosed ranges.

In some embodiments, the coating composition can include a UV absorber.UV absorbers can include those described cyano substituted butaminessuch as those described in U.S. Pat. No. 4,849,326, acetylenic compoundssuch as those described in U.S. Pat. No. 4,839,274, substituted styrenessuch as those described in U.S. Pat. No. 5,215,876, hydroxyphenylbenzotriazoles such as those described in EP 0 451 813, Schofield et al,EP 0 190 003, or U.S. Pat. No. 5,084,375, triazines such as thosedescribed in EP 0 531 258 or EP 0 530 135, cyanomethyl sulfone-derivedmerocyanines such as those described in U.S. Pat. No. 3,723,154,thiazolidones, benzotriazoles and thiazolothiazoles such as thosedescribed in U.S. Pat. No. 2,739,888, 3,253,921 or 3,250,617, triazolessuch as those described in U.S. Pat. Nos. 2,739,971, 4,783,394,5,200,307, 5,112,728, and Leppard et al EP 0 323 408, EP 0 363 820, DD288 249, U.S. Pat. No. 3,004,896, hemioxonols such as those described inWahl et al U.S. Pat. No. 3,125,597 and Weber et al U.S. Pat. No.4,045,229, acidic substituted acidic substituted methane oxonols such asdescribed in EP 0 246 553, and Liebe et al EPO 0 345 514, thedisclosures of which are hereby incorporated by reference. Inorganiccompounds such as nano-titanium dioxide can also be used. In someembodiments, the coating composition can include an amount of UVabsorber in a range in a range with a low end of >0 parts per million byweight (ppm), 500 ppm, 1000 ppm, or 1500 ppm, and an upper end of 200ppm, 2500 ppm, or 3000 ppm, based on the total weight of monomer orother polymerizable compound. All possible combinations of theabove-mentioned range endpoints (excluding impossible combinations wherea low endpoint would have a greater value than a high endpoint) areexplicitly included herein as disclosed ranges.

The aforementioned polymerizable compounds, free radicalphotoinitiators, and UV absorber may be used singly, sequentially, or incombination. From the desirability of physical properties of products,one or more classes of monomer may be chosen for the coating compositionto apply to the conductive connection interface. In some embodiments,the monomer includes one or more (meth)acrylates or acrylic acid.

The coating composition can include various additives and coating aids,as known in the art. Additives and coating aids can include, but are notlimited to dyes (static or fluorescent), surfactants, thickeners,stabilizers, pigments, fillers, and other known coating additives.

In some embodiments, the coating composition can have a viscosity at 40°C. in a range having a low limit of 100 cp, more specifically 200 cp,and more specifically 300 cp, and an upper limit of 4500 cp, morespecifically 2500 cp, and more specifically 1500 cp. All possiblecombinations of the above-mentioned range endpoints are explicitlyincluded herein as disclosed ranges. In some embodiments, the coatingcomposition can have a viscosity of 300-1000 cp at 40° C. In someembodiments, the coating composition can have a viscosity of 200-800 cpat 40° C. The viscosity of the coating composition can be manipulated byvarying respective amounts of the oligomer and monomer, with lowerviscosities promoted by higher proportions of monomer in the coatingcomposition, and higher viscosities promoted by higher proportions ofoligomer in the coating composition.

When both oligomer and monomer are present in the coating composition,the respective amounts of oligomer and monomer can vary, depending onthe target properties of the application process and the final coating.In some example embodiments, the composition can comprise at least 50wt. % oligomer and less than 100 wt. % oligomer, and greater than 0 wt.% monomer and less than or equal to 50 wt. % monomer.

In some embodiments, the coated substrate can be treated with acorrosion-inhibiting oil, which can include conventional untreatedmineral oils or a mineral oils with corrosion-inhibiting additives suchas phosphates (e.g., zinc dithiophosphate). The oil can be applied byconventional means such as with a spray or brush. Examples ofcorrosion-inhibiting oils include conventional mineral oil and othercommercially-available oils such as Ecoline 3690, Nye 531J, Nye 561J, orRichards Apex 562CPD. Application of the oil to the coated componentscan be made by various techniques, including but not limited to jet,spray, or tool-applied using tools such as brushes, sponges, or rollers.

The following examples are intended to further describe and not to limitthe present disclosure.

EXAMPLES Example 1

Coating compositions were prepared containing 70 wt. % of a urethaneacrylate oligomer (CN961H81 from Sartomer Corp.), 20 wt. % of laurylacrylate monomer, and 10 wt. % acrylic acid monomer, based on the totalweight of the coating composition. A free radical photoinitiator(H-NU-470-LT5 from Spectra Corp.) and/or a UV absorber (Tinopal OB COfrom BASF) were included in some of the coating compositions as setforth in the Table below. The coating compositions were applied to 0.75mm² Delphi cable which was terminated with a Delphi terminal #13781251,using a robotic jet coater and cured using an LED UV lamp emitting at395 nm for durations specified in the Table. The coatings were appliedto 0.75 mm² terminated aluminum cable leads in approx. 2-3 secondswithout contamination of the mating portion of the terminal. The coatedassemblies were subjected to 24 hours of exposure to an aqueous acidsolution containing 4.2 wt. % hydrochloric acid and 5 wt. % of sodiumchloride, and the aluminum content of the aqueous solution was measuredto determine the amount of aluminum lost from the wire terminalassembly.

TABLE Initiator UV Absorber UV exposure Dissolved Al Sample # (phm)(ppm) (seconds) (ppm) 1 4 0 0.35 9.4 2 4 0 0.7 29.6 3 4 0 4.0 23.0 4 100 0.5 8.4 5 10 1500 0.3 1.2 6 10 15,000 0.3 1.3

As can be seen from the results in the Table, terminals coated with thecoatings comprising higher amounts of photoinitiator had significantlyimproved performance against aluminum loss.

While the subject matter herein has been described in detail inconnection with only a limited number of embodiments, it should bereadily understood that it is not limited to such disclosed embodiments.Rather, the embodiments described herein can be modified to incorporateany number of variations, alterations, substitutions or equivalentarrangements not heretofore described, but which are commensurate withthe spirit and scope of the disclosure. Additionally, while variousembodiments have been described, it is to be understood that someimplementations may include only some of the described embodiments.Accordingly, the disclosure is not to be seen as limited by theforegoing description.

The invention claimed is:
 1. A method of sealing a wire terminalassembly comprising a conductive cable core and a conductive terminalconnected to the conductive cable core along a conductive connectioninterface, the method comprising: dispensing a coating composition overthe conductive connection interface, the coating composition comprising:(1) a polymerizable compound comprising an unsaturated bond, and (2) afree radical photoinitiator; and exposing the coating composition toactinic radiation from an actinic radiation source positioned within 10mm of the coating composition for a duration of less than 0.7 seconds.2. The method of claim 1, comprising exposing the coating composition toactinic radiation for a duration of less than 0.6 seconds.
 3. The methodof claim 1, comprising exposing the coating composition to actinicradiation for a duration of less than 0.5 seconds.
 4. The method ofclaim 1, comprising exposing the coating composition to actinicradiation for a duration of less than 0.4 seconds.
 5. The method ofclaim 1, comprising exposing the coating composition to actinicradiation for a duration of at least 0.2 seconds.
 6. The method of claim1, wherein the actinic radiation comprises UV radiation.
 7. The methodof claim 6, wherein the actinic radiation includes a peak wavelengthbetween 380 nm and 400 nm.
 8. The method of claim 1, comprising exposingthe coating composition to 0.5-16 joules of energy from the actinicradiation.
 9. The method of claim 1, wherein the coating compositioncomprises greater than 4 parts per hundred by weight of the free radicalphotoinitiator, based on the total weight of polymerizable compound. 10.The method of claim 9, wherein the coating composition comprises atleast 6 parts per hundred by weight of the free radical photoinitiator,based on the total weight of polymerizable compound.
 11. The method ofclaim 9, wherein the coating composition comprises at least 8 parts perhundred by weight of the free radical photoinitiator, based on the totalweight of polymerizable compound.
 12. The method of claim 9, wherein thecoating composition comprises at least 10 parts per hundred by weight ofthe free radical photoinitiator, based on the total weight ofpolymerizable compound.
 13. The method of claim 1, wherein the coatingcomposition comprises at least 1000 parts per million by weight of anultraviolet light absorber, based on the total weight of polymerizablecompound.
 14. The method of claim 1, wherein the coating compositionfurther comprises an oligomer comprising at least two unsaturated bonds.15. The method of claim 1, wherein the cable further comprises anelectrically insulating outer cover, from which a lead portion of thecable core extends, and wherein the conductive connection interfacecomprises a crimp connection of a structure of the terminal onto thelead portion of the cable core and a crimp connection onto theelectrically insulating outer cover.
 16. The method of claim 1, whereinthe coating has a cured thickness of 50 μm to 5 mm.
 17. The method ofclaim 1, wherein the actinic radiation comprises UV radiation.
 18. Themethod of claim 1, wherein the coating composition further comprises anoligomer comprising at least two unsaturated bonds.
 19. A method ofsealing a wire terminal assembly comprising a conductive cable core anda conductive terminal connected to the conductive cable core along aconductive connection interface, the method comprising: dispensing acoating composition over the conductive connection interface, thecoating composition comprising: (1) a polymerizable compound comprisingan unsaturated bond, (2) a free radical photoinitiator, and (3) at least1000 parts per million by weight of an ultraviolet light absorber, basedon the total weight of polymerizable compound; and exposing the coatingcomposition to actinic radiation from an actinic radiation sourcepositioned within 10 mm of the coating composition for a duration ofless than 0.7 seconds.
 20. The method of claim 19, wherein the coatingcomposition comprises at least 1500 parts per million by weight of theultraviolet light absorber, based on the total weight of polymerizablecompound.